Cryogenic liquids, such as cryogenic hydrogen, nitrogen, and oxygen, may be employed for a variety of applications. For example, cryogenic liquids may be used as fuel for aircraft or spacecraft engines, such as rocket engines. In other examples, cryogenic liquids are used to cool components of vehicles.
In most applications, cryogenic liquids are typically delivered from a liquid source to a destination via a piping arrangement. To control flow of cryogenic liquids through the piping, one or more ball valves may be included. Ball valves generally include a valve housing, a flange, and a ball. The valve housing can be placed between two pipes in the piping arrangement; alternatively, the valve housing may be disposed in an interior of a pipe. The flange couples to and defines a valve chamber with the valve housing. The ball is disposed in the valve housing and extends from a stem that is configured to rotate relative to the valve housing. As a result, the ball also rotates within the valve chamber. Typically, the ball includes a bore so that when the ball rotates to a first position, the bore provides a path for the cryogenic liquid to travel from one portion of the valve chamber to another. When the ball rotates to a second position, the opening is blocked and the cryogenic liquid is prevented from traveling through the valve chamber.
To reduce leakage within the ball valve, a seal may be disposed between the flange and the ball. Generally, the ball may comprise aluminum or another metallic material. For improved contact with the ball, the seal can be formed of a polymer material. Because the seal and ball materials have differing thermal expansion properties, they may expand at different rates as the ball valve is exposed to various temperature environments. As a result, a load provided by the metallic ball against the polymer seal may not provide a desired amount of contact or force when the ball valve is exposed to an initial temperature and then subsequently exposed to a lower temperature, such as when disposed in a room temperature environment (e.g., about 22° C.) and subsequently exposed to cryogenic fluids (e.g., fluids having temperatures less than about −150° C.). Even when the ball valve is exposed to temperatures higher than those of cryogenic fluids, the load of the ball against the seal may be excessive and unwanted friction may be produced between the ball and the seal. Accordingly, use of the ball valve may be limited to environments within a certain temperature range.
Hence, it is desirable to have an improved ball valve that provides desired sealing and load capabilities over a wide range of temperatures. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.